Air turbine motor with resiliently biased adjustable tapered bearings



W. R. HEATHE AIR TURBINE MOTOR WITH RESILIENTLY BIASED ADJUSTABLETAPERED BEARINGS A ril 30, 1968 5 Sheets-Sheet 1 Filed Oct. 1966 FlG.4

FIG.6

' I06 ea INVENTOR. WILLIAM R. HEATHE AT RNEY FIG.5

W. R. HEATHE AIR TURBINE MOTOR WITH RESILIENTLY BIASED April 30, 1968ADJUSTABLE TAPERED BEARINGS 5 Sheets-Sheet 2 Filed Oct. 5, 1966 lug! Auv MW .n Na

INVENTOR. WILLIAM R. HEATHE FIG.|2

ORNEY April 30, 1968 w. R. HEATHE 3,380,162

AIR TURBINE MOTOR WITH RESILIENTLY BIASED ADJUSTABLE TAPERED BEARINGSFiled Oct. 5, 1966 5 Sheets-Sheet 3 89 I26 I46 I52 INVENTOR. WILLIAM R.HEATHE FIG.|3

/TORNEY United States Patent 3,380,162 AIR TURBINE MOTOR WITHRESILIENTLY BIASED ADJUSTABLE TAPERED BEARINGS William R. Heathe, York,Pa., assiguor to The Dentists Supply Company of New York, York, Pa., 21corporation of New York Continuation-impart of application Ser. No.498,281, Oct. 20, 1965. This application Oct. 5, 1966, Ser. No. 584,596

16 Claims. (CI. 3227) ABSTRACT OF THE DHSCLOSURE An air turbine motorhaving a rotor on a shaft supported by combination radial and thrust:air bearings each comprising cooperating stator and rotor bearingshaving complementary tapered bearing surfaces, axial-1y variableyieldable means extending between said stator bearings, and positioningmeans operable in opposition to said variable yieldable means to movesaid one of said stator bearings axially to establish a desired runningclearance between said stator and rotor bearings.

This application is a continuation-impart of application Ser. No.498,281, file-d Oct. 20, 1965, now abandoned.

This invention pertains to a motor comprising an air turbine having ashaft supported by air bearings. Preferably, said motor structure isadapted to be of miniature size, whereby the same is highly suit-ablefor use within a dental handpiece. Specifically, the present inventionpertains particularly to air bearings of novel design supporting saidrotor and additional features associated therewith, which incidentallyinvolve certain features of the impeller of the turbine as well as otherturbine and handpiece elements incident to mounting and operating saidair bearings. The motor and air bearings comprising the presentinvention are not to be restricted to use in dental handpieces since thesame are adapted to use in various other items and mechanisms,particularly of small or miniature size and especially where highspeeds, substantially in excess of 100,000 rpm. are to 'be developed.For convenience and simplicity of illustration and description of theinvention, a dental handpiece has been selected to provide a practicalapplication for the motor and air bearings comprising the invention, butin so doing, it is not intended to restrict the invention to such use.

Various types of air bearing constructions have previously been devisedand employed in dental handpieces. For various reasons, however, thehandpieces employing these structures have not received wide acceptance,nor has the performance thereof been satisfactory from the standpoint ofavailable torque and other desirable operational characteristics, suchas instant starting, especially after the rotor has been stalled, easeof mounting the turbine .and bearings within the head of the handpiece,and ease of manufacture, to mention only some of the most salientdefects and difliculties found to be present in existing airbearing-type handpices.

It is the principal object of the present invention to provide a motorhaving a fluid-operated turbine in the housing thereof, the turbinebeing supported by air bearings comprising cooperating rotor bearingsand stator bearings, and including resilient means engageable with thestator bearings and operable primarily to yield and permit limitedmovement of said stator bearings toward each other to cause a desiredrunning clearance to be provided between said rotor and stator bearings,cooperating pairs of which are provided adjacent opposite ends of thehousing of the motor.

It is a further object of the invention to provide posi- 3,380,162.Patented Apr. 30, 1968 tioning means, preferably in the form of seats,respectively disposed in one end of the housing of the motor and in athreaded cap in the opposite end, said seats respectively engaging theoutermost end-s of the stator bearings and operable to move the sameaxially toward each other, against the force of said aforementionedresilient means, to facilitate the establishment of said runningclearance between the rotor and stator bearings of the motor as well asoperatively clamp the stator hearings in operative position under suchcircumstances.

It is a further object of the invention to provide complementarysegmental spherical surfaces respectively on said seats and upon thesurfaces of the stator bearings coengaging said seats in order toprovide appropriate limited movement of said stator hearings to permitself-seating of said bearings within said seats in a manner to provideself-aligning of the stator bearings with respect to the rotor bearingsand said seats.

Ancillary to the foregoing objects, it is a still further object toprovide simultaneous and resilient self-equalizing of the rotor bearingswith respect to the stator bearings by the use of resilient means whichpreferably comprise distortable annular springs or washers, the innerperipheries of which engage portions of the stator bearings in a mannerwhich tends constantly to urge the same axially in opposite directionsaway from each other and respectively toward the rot-0r bearings withwhich they are associated, the outer circumferences of said washersbeing maintained in constant axially spaced relationship by suitablespacing means which incidentally surround the impeller of the turbine.

It is another important object of the invention to arrange the rotor,the stator and rotor bearings, the aforementioned flexible washers andthe spacing means therefor, as a cartridge assembly capable of beingprecisely assembled at a factory, for example, and readily insertablewithin one end of the housing of the motor for reception of one end ofthe lowermost stator bearing upon a seat in the inner end of the housingof the motor, while a seat in the cap correspondingly engages the outerend of the opposite stator bearing, and running clearance between thestator and rotor bearings adjacent opposite ends of the rotor readily isestablished simply by threading the cap into a desired closingrelationship with respect to the 0pposite end of the housing of themotor from said first mentioned end, the cartridge otherwise beingreadily removable from the housing of the motor for replacement,servicing, or the like.

A still further object of the invention is to provide segmental,spherical surfaces upon thestator bearings in the regions thereof whichrespectively engage the perimeter of the central holes in the flexibleannular springs or washers so as to further facilitate self-alignment ofsaid stator bearings with respect to the rotor bearings disposed thereinand the engagement of the spherical surfaces of the stator bearings bythe perimeters of the central holes in the flexible springs and theseats in the housing and cap being such as to accurately clamp saidstator bearings in operative position after the alignment thereof hasbeen achieved.

Still another object of the invention, especially when applied to adental handpiece is to provide novel means comprising a spray annulus inthe end of the head of the handpiece nearest the end of the shaft fromwhich a cutting bur, or the like, extends.

Still other objects of the invention, especially when applied to adental handpiece are to provide certain novel and useful arrangementsfor distributing both driving air and bearing air respectively to theimpeller and air bearings, connection thereof to the supply conduitswithin a handle readily being effected in a foolproof manner by 3appropriate indexing means with respect to the aforementioned cartridgeand the interior of the head of the handpiece within which it isreceived.

Details of the foregoing objects and of the invention, as well as otherobjects thereof, are set forth in the following specification andillustrated in the accompanying drawings comprising a part thereof.

In the drawings:

FIG. 1 is a longitudinal elevation of the exterior of a dental handpieceembodying the principles of the present invention.

FIG. 2 is a fragmentary, enlarged plan view of the head end of thehandpiece illustrated in FIG. 1 as viewed on the line 2 -2 of saidfigure.

FIG. 3 is a vertical sectional elevation on a scale similar to that ofFIG. 2 and illustrating details of the head and the manner in which thecartridge comprising the rotor and air bearings therefor are disposed inoperative position within the head, said view also showing a projectionby which the head is secured to the neck of the handle of the handpiece.

FIG. 4 is a longitudinal horizontal section of the head of the handpieceas shown in FIG. 3 and as viewed on the line 44 of said figure.

FIG. 5 is a view similar to FIG. 4, but being a horizontal sectionalview taken on the line 55 of FIG. 3.

FIG. 6 is an end view of the head unit of the handpiece illustrated inFIG. 3 as seen from the line 66 of said figure.

FIG. 7 is a longitudinally exploded view of the car tridge structureshown in FIG. 3 to illustrate details of all elements thereof.

FIG. 8 is a longitudinal sectional view of the handle and neck portionof the handpiece to illustrate details especially of the air and waterdistributing arrangement therein, as well as muflling mechanism.

FIG. 9 is an enlarged transverse sectional view of the mufliing means inthe handle of the handpiece shown in FIG. 8, as viewed on the line 99 ofsaid figure.

FIG. 10 is a plan view of a combination supporting and connecting blockmounted within the handle of the handpiece intermediately of the endsthereof.

FIG. 11 is a transverse sectional view of the block shown in FIG. 10 asseen in the direction of the arrows on the veltical section line 1111shown in FIG. 10.

FIG. 12 is a view similar to FIG. 11, but showing the opposite side ofsaid block from that illustrated in FIG. 11, as seen on the line 12--12in FIG. 10.

FIG. 13 is a still further enlarged vertical sectional view of theentire head of the handpiece, including the cartridge therein andillustrating details of the same.

Referring particularly to FIGS. 1 and 8, the handpiece selected forpurposes of illustrating and describing the present invention comprisesa generally tubular handle 10 preferably formed from a plurality ofconnected sections and provided with coupling means 12 at the rear endand a neck 14 at the forward end extending angularly to the handle andto which a housing or head 16 is connected at the forward end of saidneck, preferably in a permanent manner. As best shown in FIGS. 3 and 13,the head 16 is hollow and is provided with an opening 18 at the upperend thereof, the inner walls of which are threaded. The head also has abottom 20, preferably integral with the side walls of the head, and ashaft opening 22 is formed centrally in said bottom.

The rear end portion of the handle 10 also is formed to include a mufilestructure 24, details of which are best shown in FIGS. 8 and 9. It willbe seen that the diameter of said structure is slightly greater than theremaining portion of the handle and said portion is provided with aseries of longitudinally extending slots 26 which are spacedcircumferentially around the outer end portion of the handle. Said outerend portion of the handle also is suitably socketed to receive the innerend of an exteriorly threaded coupling plug 28, which is bored inwardlyfrom the outer end to provide a transverse wall 30 through which aplurality of tubes, to be described in detail hereinafter, extend. Thewalls of the tubes preferably are sealed with respect to holes thereforprovided in the wall 30.

The rearward portion of handle 10 accommodates a longitudinallyextending conduit 32, which preferably is a metal tube and may beregarded as the main air delivery tube. The outer end thereof isconnected to a suitable source of 'air under pressure and said air istransmitted by said tube to the block 34, the forward end of conduit 32being fitted into the counter-bored hole 35, which is clearly shown inFIG. 10. Said hole extends entirely through the block 34 and terminatesin a discharge end 36, shown best in FIG. 8, which discharges air underpressure into plenum chamber 38, which comprises the interior of theneck and forward end of the handle. It extends from the block 34 to theinner surface of head plug or block 40, which preferably is integralwith the head 16 and is press-fitted or otherwise firmly secured withinthe forward end of the neck 14, such attachment being rendered air-tightby epoxy resin, solder, or otherwise.

An air-exhaust tube 42 is secured at its inner end within a bore 44, seeFIGS. 6 and 8, formed longitudinally within the head plug 40. Theopposite end of tube 42 fits into a preferably counter-bored hole 46formed beside hole in block 34, the larger end thereof extendingforwardly to receive said end of exhaust ube 42, preferably with aclose, air-tight fit employing solder, epoxy resin, or the like. Thehole 46 terminates in a discharge end 48, see FIG. 11, which freelyexhausts into the hollow interior 50 of the handle 10 which extendsbetween the block 34 and mufile structure 24. The forward end of exhausttube 42 communicates with the interior of head 16 in a manner to bedescribed.

Also extending longitudinally through handle 10 is a pair of conduittubes 52 and 54 which are of smaller capacity than conduit 32, the rearends of said tubes respectively being connected with sources of air andwater under pressure, and the forward ends thereof respectively extendinto suitable bores 56 and 58 in block 34. Supplementary tubes 60 and62, of smaller diameter than tubes 52 and 54, extend forwardly from thebores 56 and 58 and respectively are closely received and secured in airand water-tight relationship respectively with bores 64 and 66 extendingpartially and longitudinally into the head plug 40 from the terminal endthereof within the neck 14. A skeletonized spacer 63 facilitates thepositioning of tubes 42, 60 and 62 in neck 14. As will be best seen fromFIGS. 4 and 5, as well as FIG. 8, transversely extending discharge bores68 and 70 intersect bores 64 and 66 and respectively discharge air andwater into a small mixing chamber 72, which is formed in the neckhousing adjacent head 16 and directly below the head block 40 adjacentthe lower part of head 16, as best seen in FIG. 8.

Referring to FIG. 13, it will be seen that the mixing chamber 72communicates through an opening 74 with an annular manifold 76 formedaround the periphery of the bottom 20 of head 16 and having a pluralityof preferably angularly directed, circumferentially spaced dischargeports 78 arranged to discharge a spray mist of mixed water and air,under pressure, toward the operative end of the bur 80, one exemplaryillustration of which is shown in FIG. 13 in foreshortened manner.

The manifold 76 may be formed somewhat uniquely by turning or otherwiseforming an annular flange 82 integrally with the side walls of the head16, particularly where the head 16 is turned from solid bar stock upon alathe, for example, this method also being convenient for forming thesolid bottom 20 within the head 16. The annular flange 82 is madesufficiently long that when the outer end thereof is bent inwardly, suchas by an operation known as spinning, the terminal end thereof isdisposed adjacent the outer surface of bottom 20 and a liquid-tight sealis effected by applying a ring 84 of solder,

epoxy resin, or the like, between the terminal end of annular flange 82and the adjacent wall of bottom 20.

In forming the head 16 by the method referred to immediately above, suchas by turning solid bar stock upon a lathe, after the outer surface ofthe head has been suitably machined, one side thereof may be boredtransversely to receive a cylindrical plug which, when completed, willform head plug 40, and appropriately securing the plug into said bore,such as by soldering, or the like, after which the inner cavity 86 ofhead 16, as best shown in FIG. 3, may be suitably machined. This isfollowed by the drilling of the necessary holes and bores which extendlongitudinally and otherwise within and through the head plug 40, someof which have been described above and others will be describedhereinafter. Also, the threads on the interior of the top opening 18 maybe formed suitably during such operations for purposes of threadablyreceiving cap 88 which has complementary threads formed on the peripherythereof. Appropriate means such as a pair of holes 89 are formed in cap88 to permit rotation such as by a spanner wrench.

The head plug 40 is also provided with additional bores, see FIGS. 4-6,extending longitudinally thereof, the same preferably being ofrelatively small diameter, especially in comparison with the bore 44which accommodates the exhaust tube 42. These additional boresrespectively comprise driving air inlet hole 92 which is disposedadjacent one side of the head plug 40, as is clearly shown in saidfigures. In view of this arrangement of the inlet delivery hole 92, thedriving air delivered thereby from the plenum chamber 38 is dischargedsubstantially tangentially into the cavity 86 of head 16 so as toimpinge upon the vanes 94 of impeller 96 illustrated in detached mannerin FIG. 5, the mounting of which is described hereinafter.

The head plug 40 also is provided, adjacent the top and bottom thereof,with additional bores comprising inlet holes 98 and 100 whichrespectively communicate at the discharge ends thereof with upperannular manifold space 102. and lower annular manifold space 104respectively within the upper and lower portions of the head 16, detailsof the formation of which are set forth hereinafter. The inner ends ofthe bearing air inlet holes 98 and 100 each communicate freely with theair supply plenum chamber 38, whereby it will be seen that it ispreferably contemplated by the present invention to employ air of'substantially the same pressure, both to supply the air bearings, to bedescribed, and to drive the impeller of the turbine. The invention isnot to be restricted to such preferred arrangement, however. Further,the shape of the inlet end 106 of the air discharge bore 44, where itmerges with the inner cylindrical cavity 86 of head 16, is clearly shownin FIGS. 4 and 5, the same being on the opposite side of head plug 40from the delivery end 108 of the driving air inlet hole 92.

The most essential feature of the present invention comprises acartridge 109 and especially its components and function thereof. Theprincipal components are illustrated in exploded form in FIG. 7, withthe exception of cap 38, illustrated therein, which actually does-notcomprise part of said cartridge. The component elements of saidcartridge, as illustrated in FIGS. 7 and 13, comprise a tubular shaft110 upon one end of which a lower, conical rotor bearing 112 ispress-fitted, said bearing preferably having a counter-bored socket 114therein to receive one end of said shaft with a press-fit. Surroundingthe lower rotor bearing 112 is a lower stator bearing 116, details ofwhich are described hereinafter. Supporting one end of lower statorbearing 116 is a lower annular resilient and distortable spring orwasher 118, the periphery of which normally abuts the lower end ofspacing sleeve 120 which is placed upon the shaft either before or afterthe rotor impeller 96 is press-fitted upon the shaft in desiredlongitudinal position thereon.

An upper resilient and distortable spring or washer 122,

at its periphery, abuts the upper end of spacing sleeve and, tofacilitate the abutment of the opposite ends of said spacing sleeve bysaid resilient springs, the opposite ends of said sleeve compriseannular flanges directed inwardly for a short distance. Upper flexiblespring 122 receives upper stator bearing 124, which is preferablyidentical with lower stator bearing 116, said upper bearing surroundingthe upper conical rotor bearing 126 which is press-fitted onto the upperend of tubular shaft 110 at the completion of the assembly of thecartridge.

It will be seen that the rotor bearings 112 and 126 preferably aresubstantially identical, with the exception of the counter-bored socket114 formed in the lower rotor bearing 112. Both the lower and upperrotor bearings have conical exterior surfaces which respectively flareradially outward and longitudinally away from each other when mountedupon shaft 110, somewhat in hourglass arrangement. The conical angle ofthe exterior surfaces of the rotor bearings preferably are identicaland, actually, said bearings are frustro-conical in that they do notcontinue to a point.

The lower and upper stator bearings 116 and 124 preferably are formed ofself-lubricating material, such as compressed graphite or solid carbonmembers, the same being suitably machined or otherwise finished to havepreferably segmental spherical surfaces 128 on the outermost endsthereof which, as will be seen from FIG. 13, respectively engagepreferably complementary segmental spherical surfaces on the seat 130formed in the upper portion of bottom 20 of head 16, and similarlyshaped seat 132 formed on the interior of cap 32 when the cartridge 110is mounted in operative position within the inner cavity 86 of head 16.The spherical configuration of the bearing surfaces 128 and thecomplementary surfaces of the seats 130 and 132 are for purposes to bedescribed. The inner conical surfaces of stator bearings 116 and 124 areexactly complementary to the outer surfaces of rotor bearings 112 and126.

The upper and lower stator bearings 116 and 124, ad jacent the innerends thereof, are provided with additional preferably segmentalspherical surfaces 134, which adjoin short, axial and annularprojections 136 which respectively project through the central openings138 of the resilient springs 118 and 122 which, if desired, may be ofthe Belleville spring-type. Initially, they may be either flat ordished, as desired. The springs 118 and 122 also may be consideredflexible to a limited extent, especially to be flexed to a shapedistorted from the original shape, but such flexibility is not of thetype normally attributed to plastic or pliable items.

As indicated above, the outer peripheral edges of the resilient springs118 and 122 respectively abut the inwardly directed annular flanges atthe opposite ends of the spacing sleeve 120 which, preferably, is formedfrom a metal tube of suitable wall thickness and, at one side thereof, alongitudinally extending index projection 140 is pressed outwardly forslidable reception within an indexing groove 142 shown in FIG. 13 asbeing cut into the inner wall of head 16 adjacent the junction of saidhead with head plug 40.

The purpose of indexing elements 140 and 142 is to suitably alignexhaust port 144 in the side wall of spacing sleeve 120 and inlet port145 formed therein, in circumferentially spaced relationship to theexhaust port 144, as shown in FIG. 7, respectively with the inlet end106 of discharge bore 44 and the delivery end 108 of air inlet hole 92which tangentially inpinges upon the vanes of impeller 96 to rotate theentire rotor comprising said impeller, shaft 110, and the rotor bearings112 and 126 fixed thereupon. The interior of the shaft 110 alsopreferably carries a chuck 146, see FIG. 13, of any suitable design,which supports the bur 80 or other type of dental tool.

When all of the components of the cartridge 110 have been assembled inthe manner described hereinabove, it

is preferable that the coengageable, complementary conical surfaces ofboth sets of rotor and stator bearings be firmly in engagement with eachother and the pressfitting of the upper rotor bearing 126 upon tubularshaft 110 preferably is continued until the relationship substantiallyas illustrated in FIG. 13 is achieved, wherein no running clearance isshown between the stator and rotor bearings and all components of thecartridge which engage each other are substantially in firm contact andthe stator bearings are centric relative to the perimetcrs of thecentral openings 138 in springs 118 and 122. Such centric relationshipis established incident to initial assembly of the cartridge.

The stator bearings 124 and 116, when the cartridge is not mounted inhead 16, also are maintained in firm engagement with the respectiverotor bearings contained therein by the force exerted by the resilientsprings 118 and 122 through the seating of the segmental sphericalsurfaces 134 of the stator bearings within said perimeters of thecentral openings 138 in said springs. Such centric seating of the statorbearings relative to springs 118 and 122 also provides initially firmself-seating of the stator bearings 116 and 124 with respect to therotor bearings 112 and 126, whereby a precise and substantially evenalignment of the complementary conical surfaces of the rotor and statorbearings automatically is established.

It also will be seen that movement of the spacing sleeve 120 isrestrained only with respect to rotary movement and not longitudinalmovement. Under normal circumstances, substantially little or nolongitudinal movement occurs, however. The sleeve 120 nevertheless isfree to move longitudinally if required to do so, especially for verysmall increments of distance, incident to the stator bearings aligningthemselves appropriately and preferably evenly with respect to the rotorbearings when running clearance is being established therebetween.However, for purposes of separating the upper and lower manifold spaces102 and 104 from each other, it is preferred that a relatively close,but sliding, fit be provided between sleeve 120 and the inner surface ofcavity 86.

For purposes of delivering air to the complementary conical surfaces ofthe rotor and stator bearings, the stator bearings are each providedwith a similar series of air delivery ports 148, which, as can be bestseen from FIG. 4, said inlet ports are spaced, preferably evenly,circumferentially with respect to each other. A substantial number ofsuch ports are provided in each stator bearing, these being dimensionedto afford the correct supply of bearing air between the adjacent conicalsurfaces of the upper and lower sets of rotor and stator bearings afterrunning clearance is established between the same.

Air is delivered to the outer ends of the ports 148 in the statorbearings respectively from the upper and lower annular manifold spaces102 and 104, as can be best seen from FIG. 13. Also, from said figure,it can be seen that the upper and lower boundaries of said annularmanifold spaces respectively are defined by the engagement of thesegmental spherical surfaces 128 of the stator bearings with theirrespective seats in the bottom of the head 16 and the cap 88, while theopposite boundaries are defined by the resilient springs 118 and 122which actually function as lateral projections extending inward fromflanges on the oppossite ends of spacing sleeve 120 and firmly engagesurfaces 134 on stator bearings 116 and 124. As a result, it will beseen the annular manifold spaces both are formed automatically as aresult of inserting the cartridge 109 within the interior cavity 86 ofhead 16.

As indicated above, all components of the cartridge 109, when notmounted within the head 16, are in relatively firm contact with eachother, including the complementary conical surfaces of the stator androtor bearings being in non-rotatable relationship with each other. Oneof the highly advantageous features of the present invention concernsthe ease of establishing a desired running clearance between saidcomplementary conical surfaces of each pair of stator and rotorbearings, automatically and evenly, which is accomplished as follows.

When cap 88 is removed from head 16, the open upper end of head 16 is incondition to receive the cartridge 109. Upon inserting the normallylower end of the cartridge within the interior of head 16, the surface128 of lower stator bearing 116 engages seat 130 in the bottom 20 ofhead 16. The complementary segmental spherical surfaces 128 and 130readily afford centering of the lower end of cartridge 109 within thehead, such centering also being facilitated by the relatively closecomplementary nature of sleeve with respect to the inner wall of head16. The cap 88 then is threaded into the upper end of head 16 whichbrings the segmental spherical seat 132 in the cap into engagement withthe upper segmental spherical end 128 of upper stator bearing 124.

Preferably such initial engagement of the cap with the cartridge is ofrelatively light nature to permit said complementary surfaces 128 and132 to effect centering of the upper end of the cartridge with respectto the head of the handpiece, as well as place similar pressure uponcoengaged surfaces 128 and on the lower end of the cartridge and in thebottom 20 of head 16, thereby establishing the entire cartridgecoaxially within said head. Continued inward threading of the cap placesinwardly directed axial pressure upon upper stator bearing 124 whichpressure, in turn, is successively transmitted to upper resilient spring122, spacing sleeve 120, lower resilient spring 118, lower statorbearing 116, and seat 130 in bottom 20. This sequence of operationsactually primarily comprises moving seat 132 toward seat 130 and resultsin the stator bearings 116 and 118 being moved axially toward eachother. Such movement is relative to the rotor bearings 112 and 126which, being fixed axially upon shaft 110, results in spaces beingdeveloped between the pairs of stator and rotor bearings which compriserunning clearances between said bearings of each pair thereof, to formair bearings.

After development of such running clearances commences, the same isautomatically equalized between the bearings of each pair by reason ofthe identical nature of resilient springs 118 and 122 and the ability ofsleeve 120 to move axially while transmitting axial movement of theupper stator bearing to the lower stator bearing. Further, the rotor andits rotor bearings 112 and 126 are free to move axially, as a fixedunit, within the limits afforded by the running clearances between thepairs of stator and rotor bearings. Hence, the rotor offers no impedanceto such automatic and simultaneous establishment of running clearancesbetween the pairs of stator and rotor bearings.

The establishment of said running clearances is achieved by threadingthe cap 88 into the upper end of the head of the handpiece while air isdelivered under suitable pressure to the upper and lower manifold spaces102 and 104 by means of bearing inlet holes 98 and 100 in head block 40.Determining desired running clearances preferably is achieved bylistening to the sound of the rotor. For example, upon initial contactof the cap with the upper stator bearings, there are no runningclearances between the pairs of bearings and the rotor is stationary,notwithstanding the fact that driving air is being discharged againstthe vanes 94 of the rotor; such driving air all simply passes outexhaust bore 44 and the bearing air is trapped in the manifold spaces102 and 104 under such circumstances.

After the initial engagement of the cap with the upper stator bearing ofthe cartridge has effected axial centering of the cartridge within thehead'of the handpiece, as explained above, continued threading of thecap into the head causes compression of the stator bearings toward eachother, as aforesaid, thereby establishing initial spacing between eachpair of stator and rotor bearings. The discharge of driving air againstthe rotor vanes 94 initiates rotation of the rotor and thereby permitsequalizing of the clearance spaces between the pairs of bearings.However, such initial operation of the handpiece produces a high pitchedwhine and indicates that more clearance is needed to establish desiredequal running clearance between the bearings of each pair thereof.

The pitch of the complementary threads on the cap and in the upper endof the head of the handpiece is relatively fine, so as to permit preciseadjustment of the running clearances between the bearings of each pair.Accordingly, following such initial spacing of the bearings asaforesaid, a slight amount of additional threading of the cap into thehead results in desired operation and equal spacing of the bearings ofeach pair to produce a desired running clearance therebetween. When thelatter has been established, the initial whine disappears and theoperation thereafter is substantially entirely silent.

The spacing of the stator bearings from their mating rotor bearings bythe procedure just described is made possible by the equal flexing ofthe resilient annular springs 118 and 122. Such flexing of these springsalso results in producing firm clamping of the stator bearings 112 and124 between the perimeters of the central openings 138 and the seats 130and 132 in the cap and bottom of the head. Although there are spacedsegmental spherical surfaces 128 and 134 respectively adjacent oppositeends of each stator bearing, these are useful primarily in the initialseating of the cartridge components with respect to each other toestablish basic alignment of all of said cartridge components. Hence,when the pressure which establishes the running clearances of saidbearings is applied, the clamping forces exerted in opposite directionsby said spring perimeters respectively toward the bearing seats in thecap and bottom of the head are such as to firmly grip the statorbearings to hold the same against any misalignment or rotation.

In actual practice, it has been found that said perimeters and seatstend to at least minutely bite or dig into the carbon surfaces 128 and134 of the stator bearings and thus enhance said gripping of the same atsaid aforementioned axially spaced surfaces 128 and 134 of each statorbearing. After the running clearance has been established between thepairs of stator and rotor bearings as aforesaid, the cap may be securedsuitably against rotation by using any of a number of expedients such ascement, light staking, or otherwise.

Bearing air is delivered from .a suitable source, under pressure, toplenum chamber 38 and from there is discharged equally, through inletholes or ports 98 and 100 respectively to the upper and lower manifoldspaces 102 and 104. From said spaces, the bearing air is deliveredthrough the ports 148 of the stator bearings to the running clearancebetween each set of rotor and stator bearings after the same have beenestablished. Hence, it will be seen that especially when the rotor isrunning free, i.e., with no thrust being put upon the operating memberexemplified by the bur 80, the rotor, including the rotor bearings 112and 126 respectively on opposite ends thereof, will be spaced evenly, inan axial direction, between the stator bearings 116 and 124.

In view of the preferred, rather appreciable angle between the conicalsurfaces of said bearings, it also will be seen that the sets ofcooperable rotor and stator bearings effectively comprise combinationradial and thrust bearings. Also, such design of air bearings employsthe principle that, when either axial or lateral thrust is imposed uponthe shaft and, correspondingly upon the rotor bearings with respect tothe stator bearings, any tendency to decrease the running clearancebetween either pair of the bearings results in increased resistancethereto through the development of increased pressures in the remainingspace between the relatively moving bearing surfaces. However, if suchthrusts are of suflicient degree that actual frictional contact is madebetween one of the rotor bearings and its corresponding stator bearingand if such contact is hard enough, the rotor will stop, but theselflubricating nature of the stator bearings, as described above,prevents any serious danger to either the rotor or stator bearings.

The imposition of an unusually high degree of thrust against the shaft,in any direction, will result in the rotor being stopped instantly.Because of the preferred selflubricating nature of the stator bearings,however, upon relieving the shaft of such thrusts, rotation of the rotoris immediately resumed. Further, during such, usually only momentary,stopping of the rotor, continual delivery of air to both the bearingsand impeller will continue, but no harm results. Rather, such continualdelivery of air insures instantaneous starting of the rotation of therotor upon discontinuing the thrust.

While the stator bearings have been described above as being formedpreferably from compressed graphite, solid carbon, or the equivalent,and in actual practice, the rotor bearings 112 and 126 are formed fromsuitable metal such as stainless steel, brass, or the like, it is to beunderstood that the invention is not to be restricted to such materials.Actually, it is only necessary that the materials from which the statorand rotor are formed or with which they must be coated be compatibleunder the circumstances that, when frictional contact occurs between thebearings of either pair, as when overloads occur, neither hearing willsustain damage and sticking of the hearings to each other does notoccur. Hence, it is preferred that the material from which at least onebearing of each pair is formed or with which it is coated, be of aself-lubricating nature.

The air film which flows through the running clearance between the rotorand stator bearings discharges from opposite ends of said space. Withrespect to the upper pair of stator and rotor bearings, such dischargeat the upper end of the same, as viewed in FIG. 13, passes throughhorizontal space and exits through discharge port 152 in cap 88.Discharge from the opposite end of said running clearance passes intothe impeller cavity 154 within which the vanes 94 revolve and suchdischarge exits from said cavity through the discharge bore 106 fortransmission through exhaust tube 42 and then into the interior 50 ofthe handle 10. The spent driving air, upon being discharged from thevanes 94 of the impeller, likewise exits in the same manner.

With respect to the lower set of rotor and stator bearings, the spentbearing air discharging from the running clearance between said bearingsexits axially inwardly into the lower portion of impeller cavity 154, asviewed in FIG. 13. The opposite end of said running clearance dischargesinto another horizontal space 156 adjacent the lower face of rotorbearing 112, the same communicating with annular discharge opening 158which surrounds the lower end of chuck 146. It will be seen from thisfigure that the latter air discharges along the shank of the dental tooland provides .a certain amount of cooling thereof and also slightly aidsin facilitating the operation of the cooling spray of mixed air andwater which discharges from the ports 78.

Control of the delivery of bearing and driving air to the inlet end ofconduit 32 is afforded by any suitable control mechanism, notillustrated in the present drawings. Such control mechanism may be inthe form of suitable pressure-regulating valves, delivery valves, andthe like, which normally are included in a control unit mount ed eitherin a dental stand or console, or otherwise. Direct delivery of such airto a handpiece may be controlled by a foot-actuated switch or valve sothat the dentist Will have both hands free for manipulating thehandpiece and other instruments, such as a dental mirror, or the like.However, all of such control is in accord with apparatus not comprisingpart of the present invention and thus no detailed description thereofis believed to be necessary.

Because of the preferred self-lubricating nature of the stator bearings116 and 124, the need for any supplementary lubrication is eliminated,whereby it is only necessary to provide preferably dry air, underpressure, for both the bearing and driving use to the head of thehandpiece. It is preferred that the air be filtered, however, inasmuchas the running clearance between the rotor and stator bearings isexceedingly small under most circumstances and, particularly whenrunning free, i.e., without thrust upon the dental tool mounted in thechuck of the handpiece, such clearance is approximately within the rangeof between .0004" and .00045". It is to be understood, however, thatthese dimensions are in proportion to the actual size of the bearingsand primarily are indicated for illustrative purposes, rather than beingrestrictive.

To appreciate the significance of the foregoing dimensions, it isindicated that the head 16 is as small as possible in order to beaccommodated readily Within human oral cavities, including those ofchildren, as well as adults. Under such circumstances, the maximumdiameter of the head is within the range of between /s and /2" and themaximum axial dimension thereof is approximately /2";

As has been indicated above, the cartridge assembly 109 readily isinsertable within and removable from the interior cavity 86 of the head16, but, preferably, this is done at a service center or factory. Hence,if the operation of the rotor fails or it is unsatisfactory to servicethe same, it is only necessary to remove the cartridge assembly, as aunit, by unscrewing cap 88. A new or rebuilt cartridge then immediatelymay be inserted in the head 16 and the used cartridge can be servicedand/ or rebuilt in due course.

Upon insertion of the cartridge in the head, the segmental sphericalsurface 128 of the lower stator bearing 116 will engage seat 130 in thebottom .20 of. the head of the handpiece. Incident to such insertion,the indexing projection 140 is disposed in indexing groove 142 on theinterior of the head of the handpiece so as properly to align theexhaust port 144 and inlet port 145 in spacing sleeve 120 with thecorresponding ends of discharge bore 106 and inlet port 108. Lastly, itis then only necessary to thread the cap 88 into the upper end of thehead 16 for engagement of the seat 132 in cap 88 with the segmentalspherical surface 128 on the outer end of the upper stator bearing 124,such threading being continued until desired running clearance isestablished between the stator and rotor bearings, by the techniquedescribed hereinabove.

If desired, appropriate movement-determining indicia may be provided onthe cap and the adjacent rim of opening 18. Also, the fit of the threadson the cap 88 with respect to the complementary threads in the opening18 of the head preferably is reasonably tight so as to maintain suchfinal adjustment of the head when the desired running clearance has beenachieved, especially if no auxiliary locking means are utilized, such ascement, staking, or the like.

Reference also has been made in the foregoing to the provision of muffiestructure 24 at the rear end of the handle 10 of the handpiece.Considering FIG. 8, it will be seen that said muffle structure maycomprise either a series of felt-like, relatively porous elements 160suitably stacked upon the assembled conduits 32, 52 and 54 or a cylinder162 of synthetic felt or the like, capable of relatively long life, andthe inner end of which is suitably cemented to the inner ends 164 of thehollow interior of the mufiie structure 24. The outer end of thecylinder of felt 162 also is cemented, for example, to the innerend-wall 30 of the coupling means 12. If preferred, both the stack ofelements 164) and cylinder 162 may be used but if only the cylinder offelt 162 is used, it will be understood the interior will be hollow.Said cylindrical felt sleeve 162 is of suitable length to extend betweenthe opposite ends of the slots 126 in the muffle structure 24, wherebyno exhaust air, either from the bearings or the turbine, can dischargeto atmosphere Without first being diffused through the cylindrical feltsleeve 162 and/or the filter elements 160 for purposes of soundreduction.

While the invention has been described and illustrated in its severalpreferred embodiments, it should be understood that the invention is notto be limited to the precise details herein illustrated and describedsince the same may be carried out in other ways falling within the scopeof the invention as claimed.

I claim:

1. An air turbine motor comprising in combination, a housing, means onsaid housing connectable to a source of air under pressure fordeliverythereof to said housing, a rotor shaft extending coaxiallywithin said housing, impeller means on said rotor shaft intermediatel-yof the ends thereof, a pair of combination radial and thrust rotorbearings mounted on said rotor shaft and respectively extendingsimilarly in opposite directions, a pair of combination radial andthrust stator bearings supported in said housing respectively adjacentopposite ends thereof and in coaxial nested arrangement with said rotorbearings, said rotor and stator bearings respectively havingcomplementary generally tapered surfaces, axially variable yieldablemeans extending between said stator bearings and operable to exertpressure simultaneously upon the same in opposite axial directionsrelative to each other to position said bearings in desired cooperativeaxial Positions relative to said rotor bearings, positioning meanscomprising rigid seat means in one end of said housing positioned toengage one of said stator bearings and a member adjustably movableaxially in the opposite end of said housing and having rigid seat meanstherein engageable with the other stator bearing, said adjustablymovable member being operable to move said stator bearings adjustablyrelative to each other and to said rotor bearings in opposition to thepressure exerted upon said stator bearings by said axially variableyieldable means to establish and maintain a desired running clearancebetween said stator and rotor bearings to constitute air bearings, andmeans to supply air under pressure to said clearance between saidbearings and to said impeller, whereby said motor is adapted for use ina dental handpiece.

2. The motor according to claim 1 in which said coacting pairs of rotorand stator bearings have complementary substantially conical surfacesflaring outwardly and away from each other toward said opposite ends ofsaid head.

3. The motor according to claim 1 in which said axially variable meansinclude resilient means engageable with the inner end portions of saidstator bearings.

4. The motor according to claim 3 in which said axially variable meanscomprise spacing means at least part of which surround said impellermeans of said rotor.

5. The motor according to claim 1 in which said rotor and rotorbearings, stator bearings and axially variable means comprises anassembled cartridge movable as a unit for insertion within and removalfrom one end of said housing, and said positioning means being withinsaid housing and movable into engagement with the outer end portions ofsaid stator bearings against the action of said axially variable meansto establish a desired running clearance between the bearings of saidsets of nested stator and rotor bearings.

6. The motor according to claim 5 in which said adjustable member whichis movable axially in the opposite end of said housing comprises a capdetachably connected to said opposite end of said housing and has one ofsaid rigid seat means therein.

7. The motor according to claim 6 in which said seats have segmentalspherical surfaces and the portions of said stator bearings engagedthereby have complementary surfaces to permit effective alignment ofsaid stator bearings relative to said rotor bearings.

8. The motor according to claim 7 in W iich said axially variableresilient means comprise resilient members having central circularopenings and said stator bearings have additional segmental sphericalsurfaces thereon seated within the perimeters of said central openingsof said resilient means, thereby permitting adjustable seating of saidstator bearings relative thereto and self-alignment of said statorbearings relative to said rotor bearings.

9. The motor according to claim 3 in which said resilient means arerelatively flat resilient annular springs having substantially centralopenings therein.

10. The motor according to claim 9 in which said stator bearings havesegmental spherical surfaces therein respectively engaging theperipheries of the central openings of said annular springs.

11. The motor according to claim 10 in which spacing means extendaxially between and engage the outer peripheries of said springs.

12. The motor according to claim 11 in which said positioning means areoperable to move said stator bearings toward each other against theaction of said springs to establish desired running clearance betweensaid stator and rotor bearings and said spacing means being movableaxially to equalize flexing of said springs.

13. The motor according to claim 1 in which the peripheries of saidstator bearings are spaced radially inward from the interior walls ofsaid housing and said seats in opposite ends of said housingrespectively engage the outer ends of said stator bearings, projectingmeans spaced axially inward from said seats and extending radiallyoutward from said stator bearings toward the inner Walls of saidhousing, thereby to define annular air manifolds around said statorbearings between said seats and projecting means and arranged to receiveair from said air supply means, and a plurality of air passagesextending through the walls of said stator hearings to receive air fromsaid manifolds and direct it to the running clearances between saidstator and rotor bearings.

14. The motor according to claim 13 in which said projecting meanscomprise said axially variable yieldable means engaging said statorbearings and said engagement being adjacent the inner ends of saidbearin gs.

15. The motor according to claim 13 further including support meansextending from said housing and having air conducting means enteringsaid housing respectively adjacent the upper and lower ends thereof andaligned directly with said manifolds to receive air under pressuretherefrom.

16. An air turbine dental handpiece comprising in combination, anelongated handle having a head on one end thereof and means on the otherend connectable to a source of air under pressure for delivery thereofto said head, a rotor shaft extending coaxially within said head,impeller means on said rotor shaft intermediately of the ends thereof, apair of combination radial and thrust rotor bearings mounted on saidrotor shaft and respectively extending similarly in opposite directions,a pair of combination radial and thrust stator bearings supported insaid head respectively adjacent the opposite ends thereof and in coaxialnested arrangement with said rotor bearings, said rotor and statorbearings respectively having complementary generally tapered surfaces,axially variable yielda'ble means extending between said stator bearingsand operable to exert pressure simultaneously upon the same in oppositeaxial directions relative to each other to position said bearings indesired cooperative axial positions relative to said rotor bearings,positioning means comprising rigid seat means in one end of said headpositioned to engage one of said stator bearings and a member adjustablymovable axially in the opposite end of said head and having rigid seatmeans therein engageable with the other stator bearing, said adjustablymovable member being operable to move said stator bearings adjustablyrelative to each other and to said rotor bearings in 0pposition to thepressure exerted upon said stator bearings by said axially variableyieldable means to establish and maintain a desired running clearancebetween said stator and rotor bearings to constitute air bearings, meansto supply air under pressure to said clearance between said bearings andto said impeller, said head having a bottom at one end provided with acentral opening permitting access to one end of said rotor shaft forattaching of a dental tool thereto and having a diameter large enough toform an annular opening to discharge air from one of said bearingsoutwardly along said rotor shaft, and said head further including liquidspray means comprising a circular flange extending axially outward fromthe periphery of said bottom of said head and integral therewith, saidflange being turned inwardly and the inner terminal edge of said flangeengaging said bottom to define therewith an annular spacing comprising aliquid manifold, means forming a liquid-tight seal between said terminaledge of said flange and bottom, liquid inlet means formed in said flangeand connectable to a source of liquid to supply liquid to said manifold,and discharge port means formed in said flange and directed toward theaxis of said rotor shaft to permit discharge of at least one stream ofliquid from said manifold toward said axis and in a direction to beintersected by air discharging along said shaft to form a spraytherefrom.

References Cited UNITED STATES PATENTS Re. 25,964 2/1966 Williams 32-272,326,180 8/1943 Stempel 308166 XR 2,732,267 1/1956 Stover 308-166 XR3,210,848 10/1965 Bizzigotti 32--27 3,256,604 6/1966 Borden 32-28 LOUISG. MANCENE, Primary Examiner.

S. NATTER, Assistant Examiner.

